THE ORGAN OF JACOBSON IN THE RABBIT, 557 
or organ of Jacobson. ‘The lumen here is circular in transverse 
section. The superficial layer of the epithelium is made up of 
conical or cylindrical, the deepest of inverted conical cells, and be- 
tween the two are pushed in more or less numerous spindle-shaped 
cells. The glands occupy ali parts of the cavity of Jacobson’s 
cartilage except the part corresponding to its lower walls, which 
is occupied by the cavernous tissue. Compare fig. 3. 
Immediately after this point, z.e. the closed tube with circular 
lumen—but the Jacobson’s cartilage is not yet a closed capsule— 
the shape of the organ and the disposition of its parts change in 
this manner: the lumen is now oval in transverse section, 
the long diameter being placed in an upward and downward 
direction. The walls of the organ of Jacobson may consequently 
now be considered as the median and Jateral wall, and the sulci 
where the two meet will be considered, as was the case in the 
guinea-pig’s organ (see my former paper), as the wpper and lower 
suleus. The epithelium lining the lumen is stratified columnar as 
described above, except on the median wall, where it is sensory 
epithelium, the structure of which will be considered minutely 
below. The sensory epithelium is not directly continuous with 
the epithelium lining the upper and lower sulcus of the organ. 
Tn connection with the epithelium of the median wall is a lymph 
follicle of considerable size. This follicle occurring in several 
successive transverse sections it follows that we have in reality 
to do with a patch of lymph-follicles extending in a longitudinal 
direction. 
The lymph-follicle, together with the numerous bundles of the 
olfactory nerve branches (see below), occupy a great part of 
the median wall; the upper part of this wall, and the whole 
region above the upper sulcus, is filled with serows glands 
whose ducts open into the upper sulcus. The lower part of the 
median wall is occupied by a plexus of large veins which, different 
from the cavernous tissue, do not contain any non-striped 
muscle in the interstitial tissue. The part of the wall imme- 
diately below the lower sulcus is occupied by serous glands 
which send their ducts into the lower sulcus ; they are far less in 
number than those of the upper sulcus. 
The remainder of the wall of the organ of Jacobson, i. e. the 
lateral wall, 2s occupied by the cavernous tissue—a plexus of 
venous vessels or sinuses separated by, and embedded in, a mesh- 
work of bundles of what appears to be non-striped muscular 
tissue. The venous vessels extend in a longitudinal direction, 
while the bundles of muscle cells extend prevalently in a radiating 
direction from the cartilage towards the lumen of the organ. 
At this point which we are now describing the epithelium of 
the lateral wall vests on a thin layer of mucous membrane densely 
